Reciprocal changes in active and inactive renin after converting enzyme inhibition in normal man

Area of Science:

• Endocrinology
• Renal Physiology
• Pharmacology

Background:

• Converting enzyme inhibition (CEI) is known to increase renin levels.
• The precise mechanisms and time course of changes in active and inactive renin following CEI are not fully understood.
• Angiotensin II exerts negative feedback on renin release from juxtaglomerular cells.

Purpose of the Study:

• To investigate the time-dependent changes in active and inactive renin following CEI.
• To differentiate between renal and plasma effects of CEI on renin levels.
• To explore the potential role of inactive renin as a precursor to active renin.

Main Methods:

• Seven healthy volunteers received a single oral dose of captopril (acute phase) followed by chronic dosing.
• Blood pressure, active renin, and inactive renin levels were measured at various time points.
• Comparative study in patients with renal insufficiency and hyporeninemic hypoaldosteronism.

Main Results:

• Acute CEI led to a significant decrease in blood pressure and a rapid increase in active renin, with a reciprocal decrease in inactive renin.
• Chronic CEI resulted in sustained elevation of active renin and a significant increase in inactive renin levels.
• Patients with renal insufficiency showed no significant changes in active or inactive renin after captopril administration.

Conclusions:

• CEI acutely increases active renin while suppressing inactive renin, with a subsequent chronic increase in both forms.
• The observed changes in renin are primarily mediated by the kidney rather than being a plasma phenomenon.
• Inactive renin may serve as a precursor for circulating active renin, particularly under conditions of CEI.